Draft genome sequence of Streptomyces tunisialbus DSM 105760T.

Streptomyces strains are well known as promising source of bioactive secondary metabolites, important in ecology, biotechnology and medicine. In this study, we present the draft genome of the new type strain Streptomyces tunisialbus DSM 105760T (= JCM 32165T), a rhizospheric bacterium with antimicrobial activity. The genome is 6,880,753 bp in size (average GC content, 71.85%) and encodes 5802 protein-coding genes. Preliminary analysis with antiSMASH 5.1.2. reveals 34 predicted gene clusters for the synthesis of potential secondary metabolites, which was compared with those of Streptomyces varsoviensis NRRL ISP-5346.

Isolation, Characterization and Chemical Synthesis of Large Spectrum Antimicrobial Cyclic Dipeptide (l-leu-l-pro) from Streptomyces misionensisV16R3Y1 Bacteria Extracts. A Novel 1H NMR Metabolomic Approach.

Streptomyces is the most frequently described genus of Actinomycetes, a producer of biologically active secondary metabolites. Indeed, the Streptomyces species produces about 70% of antibiotics and 60% of antifungal molecules used in agriculture. Our study was carried out with the goal of isolating and identifying antimicrobial secondary metabolites from Streptomyces misionensisV16R3Y1 isolated from the date palm rhizosphere (southern Tunisia). This strain presented a broad range of antifungal activity against Fusarium oxysporum, Aspergillus flavus, Penicillium expansum, Aspergillus niger, Candida albicans, Candida metapsilosis, and Candida parapsilosis and antibacterial activity against human pathogenic bacteria, including Escherichia fergusonii, Staphylococcus aureus, Salmonella enterica, Enterococcus faecalis, Bacillus cereus and Pseudomonas aeruginosa. The purification procedure entailed ethyl acetate extract, silica gel column, and thin layer chromatography. Based on 1H NMR metabolomic procedure application, also supported by the GC-MS analysis, cyclic dipeptide (l-Leucyl-l-Proline) was identified as the major compound in the bioactive fraction. In order to confirm the identity of the active compound and to have a large quantity thereof, a chemical synthesis of the cyclic dipeptide was performed. The synthetic compound was obtained with a very good yield (50%) and presented almost the same effect compared to the extracted fraction. This study indicates for the first time that Streptomyces misionensis V16R3Y1 exhibits a broad spectrum of antimicrobial activities, produced cyclic dipeptide (l-Leucyl-l-Proline) and might have potential use as a natural agent for pharmaceutical and agri-food applications.